Coated fibrous sheet materials



Patented Sept. 3, 1940 UNITED STATES 2,213,843 COATED FIBROUS SHEETMATERIALS William -H. Alton, Westport, Conn., assignor to R. T.Vanderbilt Company, Incorporated, New g York, N. Y., a corporation ofNew York J No Drawing. Application October 11, 1938, v 1

Serial No. 234,398 Y Claims.

This invention relates to the coating and filling of fibrous, sheetmaterials, such as paper, textiles and the like; and it relates moreparticularly to the coating or filling of paper or textitles withwater-resistant materials to impart thereto a water resistant finishwhich is very durable, which is highly resistant to decomposition and tohigh temperatures, etc. Textiles, such as cotton fabrics, filled orcoated in accordance with the invention, are water resistant to theextent that the coating or filling composition is not readily removed bywater as in washing, and the coating or filling is highly resistant todeterioration because of exposure to the weather. Such textiles,properly treated in accordance with the invention, may be highly waterabsorptive and have advantages over previously known filled or coatedtextiles for certain purposes where high water absorption is desired;

or the textiles may be highly resistant to water penetration, i. e.quite waterproof.

In accordance with the present invention, paper, textiles and the likeincluding such fabrics as cotton fabrics and glass cloth, are filled orcoated with a composition including a waterswellable colloidal hydroussilicate of aluminum, calcium, or magnesium, or a complex waterswellablecolloidal hydrous silicate of more than one of these metals, and anemulsified synthetic resin, the water-swellable hydrous silicate and theresin being applied in the form of an aqueous slurry or suspension,containing the emulsified resin, and the suspended silicate. Thecompositions may, of course, include other materials commonly used inthe coating or filling of textiles and paper, such as adhesivesincluding starch, casein, or the well known casein substitutes, or addedminerals, including the various clays, calcium carbonates, calciumsulfates, etc. In -some cases the water-swellable hydrous colloidalsilicate may naturally occur in admixture with minerals such ascarbonates which are sufliciently soft to permit pulverizationto-impalpable fineness, and in such cases the water-swellable silicatesmay be used without separation of the admixed mineral.

The water-swellable silicate-synthetic resin emulsion compositions haveimportant advantages for the back filling of fabrics of open weave wherewashability or resistance to heat and moisture is desired, as in shoelinings, etc. Closely woven fabrics are ordinarily finished bystarching" instead of filling, and the silicate-resin emulsioncompositions have outstanding advantages for such finishing of fabrics,because, when applied to fabrics, they do not readily wash out.

- and they impart to the cloth a finished or feel which is free from theobjectionable clamminess of fabrics finished with starch. Glass textilesare more or less widely used for electrical insulation purposes; but ithas not been found possible -to weave a fabric sufliciently tight toprevent current leakage through the interstices of the fabric; It hasbeen proposed to prevent such current leakage by filling between thethreads of the fabric with varnish, but thevarnish melts and carbonizesat the temperatures to which such insulating material is commonlyheated. Glass fabrics filled with the silicate-resin composition showgreatly improved properties for electrical insulation, because of thegreat resistance to decomposition at high temperatures, glass fabrics sofilled showing no decomposition or deterioration at temperatures up to500 F. or higher. For certain purposes, such as bandages and the like,fabrics are desired which are entirely water absorbent; and for suchpurposes, fabrics may be filled with water-swellable silicate-resincompositions which have important advantages, both because they retainthe natural porosity of the cloth and because the water-,

swellable silicate has the property of absorbing substantial amounts ofwater.

Textiles or paper filled or coated in accordance withthis invention arequite flexible and pliable and are notharsh and stifl" to the extentthat they crack where folded. The filling or coating is not brittle, anddoes not. fall out when the material is bent, nor readily fall out onrepeated folding of the material.

The water-swellable silicates used in preparing the coating, filling andfinishing compositions may be obtained from various sources. In general,they belong to the Montmorillinite group of minerals, which includesMontmorillinite, Beidellite, Nontronite and Saponite. They occiir innature in admixture with various other mineral products, and in somecases it is important to removesoxne of the other mineral productsbefore using the water-swellable hydrous silicates, whereas in othercases, such removal is unnecessary. Where the water-swellable hydrouscalcium-magnesium-aluminum silicates, which ocour in bentonite, areused, it is important to separate and discard the gritty, material withwhich such silicates are usually associated; and this separation may bereadily obtained centrifugally, with the subjection of a slurry orsuspension of bentonite in water containing from around 4 to 15% or moreof solids to a centrifugal force ranging from about 400 to 1500' or moretimes the force of gravity, as described in the application of WilliamH. Alton, Serial No. 174,859," filed November 16, 1937. Where the'water-swellable silicates used occur naturally in admixture withcarbonates, etc., itmay be desirable to separate the carbonates from thesilicates by a similar process, as described in the consistingsubstantially entirely of water-swellable, hydrous colloidal silicate isused in preparing the coating, filling and finishing compositions,particularly where a highly absorptive composi tion is desired. On theother hand, for many, if not most, purposes, the presence of suchextraneous minerals as calcium carbonate or magnesium carbonate isunobjectionable, because these minerals are soft, may be readilypulverized to an extremely finely divided state, and do not abrade orwear machinery as do the gritty particleawhich occur in commercialbentonite.

It is important and. advantageous to use a water-swellable silicate of alight, advantageously white, color. Some silicates, derivedfromavailable sources, are not well suited for use in accordance withthe present-invention because of their dark color, particularly where itis desired to obtain white or lightcolored paper or textiles. Coloringmaterials may, of course, be included in the compositions.

A wide range-of synthetic resins may be used in forming the resinemulsions used in the coating, filling and finishing compositions.Advantageously the resins are used by forming an aqueous emulsion ofvthe resin, and admixing such aqueous emulsion with a slurry orsuspension of the water-swellable silicate. The resulting aqueouscomposition, containing the emulsified resin 'and the suspendedsilicate, thus being a composite suspension and emulsion, is extremelystable, and shows practically no tendency to settle out, providing therelative proportions of the silicate and the resin are properlyadjusted. It is important that the amount of resin in the compositiondoes not greatly exceed the amount of bentonite, in order to producesatisfactory coatings or finishings, and to have proper stability of thecomposition.

Among the synthetic resins which may be emulsified with water for useincarrying out the invention are the alkyd resins, that is, the resinsderived from a polyhydric alcohol, a polybasic acid and a modifyingagent, such as a fatty acid, particularly the fatty acids derived fromdrying oils, the acrylic acid and acrylic acid ester resins, obtained bythe polymerization of acrylic acid or acrylic acid esters, the cumarresins, the 'vinyl resins, obtained by polymeriza tion of vinylcompounds, the phenol resins, the modified phenol resins, such as theresins obtained from phenol resins and ester gum, copal' or the like,the ureaor thiourea-formaldehyde resins, etc. Of course, mixtures of thevarious resins, such as mixtures of the alkyd resins and the phenolresins, or the alkyd resins and the urea-formaldehyde resins, orothermixtures of compatible resins may be used. In general, the resinsshould be of a light color, advantageously as colorless and transparentas possible, particularly where light or white paper or textiles aredesired.

The resin emulsions are readily produced by the emulsification of theresins with water with the aid of an alkaline emulsifying agent,suchasammonia, triethanolamine, morpholine, sodium like.

Ordinarily, the mix-.

cold. Methods of producing emulsions oi the glyptalresins, that is, theglycerin-phthalic an-' hydride resins, unmodified by other agents suchas fatty,acids or the like, do not have properties which make themuseful because they do not form emulsions with alkaline emulsifyingagents and form films which soften in water and dissolve in dilutealkaline solution and hence are not resistant to laundering operationsor the Nevertheless, for the coating of paper. and for other purposeswhere washability is'not required, even these resins may .be used incarrying out the invention, particularly when used in admixture withother resins, such as rosin, ester gum, copal, phenolic resins, eitherstraight or modified, urea-formaldehyde resins, etc.

In forming the water emulsions, there is no critical range ofproportions of solids to water. It is convenient to prepare theemulsions with a solid content of about although they may be varied overa wide range, as is understood in the art.

The coating compositions containing the water-swellable hydrous silicateand the emulsified resin for most filling, finishing and coatingpurposes should contain in the neighborhood of or smaller amounts of theresins, and may contain other admixed materials, such as other minerals,including those which may occur in natural admixture with the silicates,starch, clays, casein or casein substitutes, etc. In general.compositions containing more than 4 to 5% of the water-swellablesilicates present difficulties in application, because of theirviscosity, as the silicates .form a viscous paste with water, par-'ticularly where the proportion of the silicate to water is in excess of4 or 5%. The other ingredients, such as the emulsified resins, etc., donot greatly effect the viscosity of the compositions in the proportionsused.

The relative proportions of resin and waterswellable silicates in thecompositions may be varied over a relatively wide range, and therelative proportions used will depend to a large extent on the nature ofthe material coated or filled, and the characteristics desired. Forexample, for filling cloth intended for window shades and the like, arelatively high proportion of resin will be used, so that the filledfabric will be resistant to water penetration. For such purposes, theresin and water-swellable silicate may be used in about equalproportions, or the amount of resin may be somewhat in excess of theamount of silicate, for example, about twice as much. Where awater-absorbent product is desired, the resin should be used in smalleramounts, for example in amounts ranging from It; to the amount of thewater-swellable silicate; that is, in amounts just suflicient to preventthe silicate from being readily removed by washing, exposure to water,etc; For coating paper, substantially the same considerations apply. Ifthe paper is to be highly resistant to penetration by water, arelatively large proportion of resin should be used, for example, anamount equal to, or a little greater than the amount of water-swellablesilicate. On the other hand, use of smaller proportions of resin resultsin the production of coated papers having less resistance to penetrationby water, but having high resistance to penetration by oil and oilymaterials, with the coating having 3 to 5% of the water-swellablesilicate, and equal 3 copal.

excellent adhesion. In no case should the resinbe used in amounts suchthat the water-swellable silicate is a minor constituent of thecomposition, for example, in amounts ranging from 5 to 10 times theamount. of silicate, as compositions containing such proportions ofresin and silicate in'efiect varnish the textile or paper, and give aproduct quite'different in nature from the products of this invention.

The invention will be further illustrated by the following specificexamples, although it is not limited thereto.

Example 1.-'A fabric intended for shoe linings is filled with acomposition consisting of an aqueous suspension or emulsion containingabout 4% of bentonite freed from gritty materials by centrifugaltreatment as described and about 3 tov 4% of an acrylic acid resin or amethyl or ethyl acrylate resin, the resin being formed into an emulsioncontaining about 25% solids and this emulsion being added to a bentonitesuspension, with dilution of the resulting composition if required. Theresulting filled fabric has the proper stiffness and a desirable texturefor shoe linings,

has no clammy feel, and does not decompose or mold because of heat ormoisture.

Example 2.An open-'weave fabric is backfilled with a composition-madefrom about 110 parts of a 7% suspension of potato flour, about 50 partsof an emulsion of an acrylate or acrylate ester resin containing about25% solids and about 40 parts of a 13% suspension of bentonite freedfrom grit in water, with dilution of the resulting composition to thedesired consistency for backfilling with available equipment. Fabric sobackfilled has an excellent'finish, and is highly resistant to removalof the filling by washing or exposure to weather.

Example 3.--A closely woven fabric is finished with the use of anaqueous composition containing about 3% of a. water-swellable silicatehaving a white color, from 2 to 3% of 'a synthetic resin, such as anacrylate or acrylic acid ester resin. or an alkydresin, or aphenol-formaldehyde resin, or a cumar resin, or a ureaorthiourea-formaldehyde resin, or a mixture of two or more of theseresins, or a mixture of one or more of these resins with a product suchas ester gum, rosin or The composition may also contain up to 3 or 4% offinely divided mineral matter, such as calcium or magnesium carbonate,which may be introduced into the combination as a naturally occurringmixture with the water-swelling silicate. The fabric so finished iswashable, is free from any clammy or disagreeable feeling on contactwith the body, and has an excellent appearance.

, 3 to 4% of emulsified alkyd resin. The paper produced is smooth andhas an excellent finish, with a coating which adheres well, even whenthe paper is folded or bent.

Example 5.-A glass fabric, intended for electrical'insulation, is filledwith the use of an aque- I ous composition containing about 3 to 5% of awater-swellable mixed calcium and magnesium silicate and about 2% ofemulsified alkyd resin. The filled fabric has excellent electricalinsulating properties and resistance to decomposition at hightemperatures- The coating and filling compositions may containdyestufis, pigments, etc. compatible with the other ingredients to colorthe textile or paper, as

well as other modifying agents, such as latex, etc.

I claim: 1. The process of treating fibrous sheet materials whichcomprises applying thereto an aqueous composition comprising awater-swellalble colloidal silicate and an emulsified synthetic resin,

the proportion of resin to water-swellable sili-.

cate not exceeding" about two.

2. The process of treating fibrous sheet materials which comprisesapplying thereto'an aqueous composition. comprising a water-swellablecolloidal silicate and an emulsified synthetic resin, the amount ofwater-swellable silicate in such composition being at least as great asthe amount of resin.

3. The process of treating fibrous sheet ma.-

terials which comprises applying thereto an aque- 5. The process oftreating fibrous sheet ma-, terials which comprises applying thereto anaque-, ous composition comprising a walter-swellable.

colloidal mixed calcium and magnesium silicate, calcium and magnesiumcarbonate, and an emulsified synthetic resin, the proportion of resin towater-swellable silicate not exceeding about two.

6. Fibrous sheet materia having applied thereto a composition includinga water-swellable colloidal silicate and a synthetic resin, theproportion of resin to water-swellable' silicate not exceeding abouttwo.

7. Fibrous sheet material having applied thereto a compositioncomprising a water-swellable silicate and a synthetic resin, the amountof resin not exceeding the amount of water-swellablesilicate. a

8. Fibrous sheet material having applied thereto a composition includinga watereswellable colloidal silicate from the group consisting ofwatersweilable aluminum, calcium and magnesium silicates and a syntheticresin, the proportion of resin to water-swellable silicate not exceedingabout two.

"9. Fibrous sheet material having applied thereto a compositioncomprising a water-swellable colloidal mixed calcium and magnesiumsilicate and a synthetic resin, the proportion of resin towater-swellable silicate not exceeding about two. 10. Fibrous sheetmaterial having applied thereto a composition comprising awater-swellable colloidal mixed cal .um and magnesium silicate, calciumand magnesium carbonate, and a. synthetic resin, the proportion of resinto waterswellable silicate not exceeding about two.

WILLIAM H. ALTON.

